System and method for providing a clean environment in an electron-optical system

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims benefit under 35 U.S.C. § 119(e) and constitutes a regular (non-provisional) patent application of U.S. Provisional Application Ser. No. 62/166,691, filed May 27, 2015, entitled MINIATURE PARTICLE OPTICAL ELEMENTS COMPRISED OF NON-EVAPORABLE GETTER MATERIALS, naming William George Schultz, Gildardo Rios Delgado and Garry Allen Rose as inventors, which is incorporated herein by reference in the entirety.

TECHNICAL FIELD

The present invention generally relates to electron-optical systems and, in particular, an electron-optical system equipped with a non-evaporable getter material for removing contaminants from the electron-optical system and locally reducing partial pressures of reactive gases in regions difficult-to-pump regions.

BACKGROUND

As electron-optic device size becomes ever smaller, it becomes more difficult to implement a controlled vacuum environment within a given electron-optical system. One such electron-optical system is that of a “miniature” electron-optical system, whereby one or more components of the electron-optical system, such as electron source or electron-optical column components, are significantly compact and positioned closely together. Further, in the case of a miniature electron-optical system, limited clearance space within the system limits the usefulness of traditional vacuum technologies. For instance, miniature electron-optical systems often have limited clearance space, often on the order of microns, between the electron emitter (e.g., carbon nanotube tube emitter) and the corresponding extractor of the electron source, making it difficult to control the vacuum environment within the region near the electron emitter and the extractor. It would be advantageous to provide a system and method that provides improved control of the vacuum environment of such electron-optical systems.

SUMMARY

An electron-optical apparatus with passive contaminant removal capabilities is disclosed, in accordance with one or more illustrative embodiments of the present disclosure. In one illustrative embodiment, the apparatus includes an electron source. In another illustrative embodiment, the apparatus includes an electron-optical column including a set of electron-optical elements configured to direct an electron beam onto a sample. In another illustrative embodiment, the apparatus includes a detector assembly configured to detect an electron signal emanating from a surface of the sample. In one illustrative embodiment, at least one of the electron source, the electron-optical column or the detector assembly includes an electron-optical element formed from a non-evaporable getter material. In another illustrative embodiment, the non-evaporable getter material absorbs one or more contaminants located within a cavity of at least one of the electron source, electron-optical column or the detector assembly.

An electron extractor for absorbing contaminants is disclosed, in accordance with one or more illustrative embodiments of the present disclosure. In one illustrative embodiment, the electron extractor includes a body. In one illustrative embodiment, the body of the electron extractor is formed from one or more non-evaporable getter materials. In one illustrative embodiment, the one or more non-evaporable getter materials absorb one or more contaminants contained within a region proximate to the body of the electron extractor. In another illustrative embodiment, the body of the electron extractor is further configured to extract electrons from one or more emitters positioned proximate to the body of the electron extractor.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not necessarily restrictive of the invention as claimed. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and together with the general description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The numerous advantages of the disclosure may be better understood by those skilled in the art by reference to the accompanying figures in which:

<figref idref="DRAWINGS">FIG. 1A</figref> is a high level schematic illustration of an electron-optical system including an electron extractor formed from a non-evaporable getter material, in accordance with one or more embodiments of the present disclosure.

<figref idref="DRAWINGS">FIG. 1B</figref> is a high level schematic illustration of an electron beam source including an electron extractor formed from a non-evaporable getter material, in accordance with one or more embodiments of the present disclosure.

<figref idref="DRAWINGS">FIG. 1C</figref> is a high level schematic illustration of an electron-optical system including an electron extractor formed from a non-evaporable getter material, in accordance with one or more embodiments of the present disclosure.

<figref idref="DRAWINGS">FIG. 1D</figref> is a high level schematic illustration of an electron-optical system including an electron extractor formed from a non-evaporable getter material, in accordance with one or more embodiments of the present disclosure.

<figref idref="DRAWINGS">FIG. 1E</figref> is a high level schematic illustration of an electron extractor equipped with a resistive heating device for activating the non-evaporable getter material of the electron extractor via resistive heating, in accordance with one or more embodiments of the present disclosure.

<figref idref="DRAWINGS">FIG. 1F</figref> is a high level schematic illustration of an electron extractor equipped with an induction coil for activating the non-evaporable getter material of the electron extractor via inductive heating, in accordance with one or more embodiments of the present disclosure.

<figref idref="DRAWINGS">FIG. 1G</figref> is a high level schematic illustration of an electron extractor equipped with a light source for activating the non-evaporable getter material of the electron extractor via light absorption, in accordance with one or more embodiments of the present disclosure.

<figref idref="DRAWINGS">FIG. 1H</figref> is a high level schematic illustration of an electron-optical system including a set of deflectors of the electron-optical column formed from a non-evaporable getter material, in accordance with one or more embodiments of the present disclosure.

<figref idref="DRAWINGS">FIG. 1I</figref> is a high level schematic illustration of an electron-optical system including an astigmatism compensator formed from a non-evaporable getter material, in accordance with one or more embodiments of the present disclosure.

<figref idref="DRAWINGS">FIG. 1J</figref> is a high level schematic illustration of an electron-optical system including a current or beam limiting aperture formed from a non-evaporable getter material, in accordance with one or more embodiments of the present disclosure.

<figref idref="DRAWINGS">FIG. 1K</figref> is a high level schematic illustration of an electron-optical system including a soft electron extractor formed from a non-evaporable getter material, in accordance with one or more embodiments of the present disclosure.

<figref idref="DRAWINGS">FIG. 1L</figref> is a high level schematic illustration of an electron-optical system including an out-of-column detector assembly including one or more components formed from a non-evaporable getter material, in accordance with one or more embodiments of the present disclosure.

<figref idref="DRAWINGS">FIG. 1M</figref> is a high level schematic illustration of an electron-optical system including an in-column detector assembly including one or more components formed from a non-evaporable getter material, in accordance with one or more embodiments of the present disclosure.

<figref idref="DRAWINGS">FIG. 2</figref> is a process flow diagram illustrating a method of forming a non-evaporable getter element, in accordance with one or more embodiments of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the subject matter disclosed, which is illustrated in the accompanying drawings.

Referring generally to <figref idref="DRAWINGS">FIGS. 1A through 2</figref>, an electron-optical system including one or more electron-optical elements formed from a non-evaporable getter material and a method of forming the same are described, in accordance with the present disclosure.

It has been observed that considerable volumes of contaminants, such as, but not limited to, volatile organic compounds, water and/or other contaminants may be generated inside electron-optical systems. The contaminants generated within an electron-optical system, such as a miniature electron-optical system, may significantly contribute to emission instability of the electron-optical system. Further, in the case of a miniature electron-optical system, limited clearance space within the system restricts the removal of the contaminants via normal approaches, such as one or more vacuum technologies.

Embodiments of the present disclosure are directed to improving the stability of high brightness particle optic sources and systems through the implementation of non-evaporable getter (NEG) materials to fabricate components of the electron-optical system in close proximity to the vacuum environment of concern. The components of the electron-optical system formed from the non-evaporable getter materials may act to passively uptake (via chemical absorption and/or adsorption) one or more gaseous contaminants within the vacuum environment. In addition, the non-evaporable getter materials may also serve to reduce partial pressures of reactive gases in regions of the electron-optical system that are difficult to pump using conventional pumping approaches. Additional embodiments are directed to the formation of additional discrete components of the electron-optical system with a non-evaporable getter material.

For the purposes of the present disclosure, a “getter material” is considered to be a material capable of absorbing one or more selected contaminants and a “getter element” is a component of an electron-optical system formed from the selected getter material. Moreover, the term “non-evaporable getter materials” is interpreted to mean getter materials which do not readily evaporate when exposed to a vacuum environment.

Additional embodiments of the present disclosure are directed to providing a clean environment within the electron-optical system by forming one or more components of the electron-optical system, such as, but not limited to, a component of an electron source or one or more electron-optical elements of an electron-optical column, from a non-evaporable getter material. Such components may include one or more electron-optical elements of the electron-optical system. For the purposes of the present disclosure a non-evaporable getter element is interpreted to mean an electron-optical element formed from a non-evaporable getter material. In this regard, a non-evaporable getter element of the present disclosure serves at least the following functions: i) operating as an electron-optical element of the system; and ii) operating as a pumping component to eliminate or reduce contaminants within the system.

The embodiments of the present disclosure are particularly useful in the context of miniature electron-optical systems due to the difficulties associated with removing gas and gaseous contaminants from miniature electron-optical systems via traditional means and the heightened cleanness requirements of miniature electron-optical systems. Miniature electron-optical systems are characterized as such due to one or more sub-millimeter, micron-sized (or smaller) electron-optical elements.

The use of a getter material is generally described in U.S. Pat. No. 5,903,098, issued on May 11, 1999; U.S. Pat. No. 6,507,146, issued on Jan. 14, 2003; U.S. Pat. No. 6,545,396, issued on Apr. 8, 2003; U.S. Pat. No. 6,917,156, issued on Jul. 12, 2005; and U.S. Pat. No. 7,550,913, issued on Jun. 23, 2009; and EPO Patent Application No. 0,736,891 B1, published on Sep. 16, 1998, which are each incorporated herein by reference in their entirety. The use of a sintered getter in a scanning electron microscope is generally described in U.S. Pat. No. 5,150,001, issued on Sep. 22, 1992, which is incorporated herein by reference in its entirety. The use of a getter material in an electron emitter is generally described in U.S. Pat. No. 6,465,954, issued on Oct. 15, 2002; U.S. Pat. No. 6,741,017, issued on May 25, 2004; and U.S. Patent Publication No. 2008/0042547, published on Feb. 21, 2008, which are each incorporated herein by reference in their entirety. The use of a getter material in a carbon nanostructure field emitter is generally described in U.S. Pat. No. 7,608,824, issued on Oct. 27, 2009, which is incorporated herein by reference in its entirety. The use of a getter material in a cold emitter x-ray tube is generally described in U.S. Patent Application Publication No. 2003/0002627, published on Jan. 2, 2003, which is incorporated herein by reference in its entirety.

The use of a getter material in a field emission display is generally described in U.S. Pat. No. 5,223,766, issued on Jun. 29, 1993; U.S. Pat. No. 5,789,859, issued on Aug. 4, 1998; U.S. Pat. No. 5,583,393, issued on Dec. 10, 1996; U.S. Pat. No. 6,127,777, issued on Oct. 3, 2000; U.S. Pat. No. 7,745,995, issued on Jun. 29, 2010; and U.S. Pat. No. 8,766,542, issued on Jul. 1, 2014, which are each incorporated herein by reference in their entirety.

<figref idref="DRAWINGS">FIG. 1A</figref> illustrates an electron-optical system <b>100</b>, in accordance with one or more embodiments of the present disclosure. In one embodiment, the electron-optical system <b>100</b> is a miniature electron-optical system. In another embodiment, the electron-optical system <b>100</b> is a miniature scanning electron microscopy (SEM) system. While the present disclosure largely focuses on an electron-optical arrangement associated with a miniature SEM system, it is noted herein that this does not represent a limitation on the scope of the present disclosure and is provided merely for illustrative purposes. It is contemplated herein that the embodiments described throughout the present disclosure may be extended to any electron-optical system configuration known in the art.

In one embodiment, the system <b>100</b> includes an electron beam source <b>102</b>. In another embodiment, the system <b>100</b> includes an electron-optical column <b>106</b> for directing and/or focusing the electron beam <b>104</b> onto a sample <b>110</b>. In another embodiment, the system <b>100</b> includes an electron detector assembly <b>126</b> for detecting one or more electron signals <b>124</b> emitted or scattered from the surface of the sample <b>110</b>. As noted previously herein, one or more components of the electron source <b>102</b>, the electron-optical column <b>106</b> and/or the detector assembly <b>126</b> are formed from a non-evaporable getter material.

The electron beam source <b>102</b> may include any electron beam source suitable for generating one or more electron beams <b>104</b>. In one embodiment, the electron beam source <b>102</b> includes one or more electron emitters <b>108</b>. For example, the one or more electron emitters <b>108</b> may include a single electron emitter. By way of another example, the one or more electron emitters <b>108</b> may include multiple electron emitters. The one or more electron emitters <b>108</b> may include any electron emitter known in the art of electron emission. For example, the one or more emitters <b>108</b> may include, but are not limited to, one or more field emission guns (FEGs). By way of another example, the one or more field emission guns may include, but are not limited to, a carbon nanotube emitter, a nanostructured carbon film emitter, a Muller-type emitter, a Spindt-type emitter, or a Schottky-type emitter.

In another embodiment, the electron beam source <b>102</b> includes one or more extractors <b>118</b> (or extractor electrodes). During operation, the one or more extractors <b>118</b> extract at least a portion of the electron beam <b>104</b> from the one or more electron emitters <b>108</b> and transmit the electron beam to the electron-optical column <b>106</b>, which in turn directs the beam to the sample <b>110</b> disposed on sample stage <b>112</b>.

The one or more extractors <b>118</b> of the electron beam source <b>102</b> may include any electron beam extractor configuration known in the art. For example, the electron beam extractor <b>118</b> may include a planar extractor. By way of another example, the electron beam extractor <b>118</b> may include a non-planar extractor. The use of a planar and non-planar extractor in an electron beam source is generally described in U.S. Pat. No. 8,513,619, issued on Aug. 20, 2013, which is incorporated herein by reference in its entirety.

<figref idref="DRAWINGS">FIG. 1B</figref> illustrates a cross-sectional view of an electron beam source <b>102</b>, in accordance with one or more embodiments of the present disclosure. In one embodiment, as shown in <figref idref="DRAWINGS">FIG. 1B</figref>, the extractor <b>118</b> of the electron beam source <b>102</b> is a non-planar extractor <b>118</b>.

In one embodiment, the non-planar extractor <b>118</b> includes an outer radius <b>130</b>. In another embodiment, the extractor <b>118</b> includes a rounded portion <b>134</b>. For example, the interior curve of the rounded portion <b>134</b> may form the opening surface to the extractor opening <b>138</b> in the emitter region <b>136</b>. In another embodiment, the extractor <b>118</b> includes an outer sloped surface <b>132</b> between the rounded portion <b>134</b> and the outer radius <b>130</b>. For instance, the outer sloped surface <b>132</b> may slope downward from the rounded portion <b>134</b> to the outer radius <b>130</b>. Such a configuration may be referred to herein as a “volcano-shaped” extractor. In another embodiment, the extractor <b>118</b> may take on a conical-shape.

It is noted herein that the scope of the present disclosure is not limited to the configuration depicted in <figref idref="DRAWINGS">FIG. 1B</figref>, which is provided merely for illustrative purposes. Rather, the shape of the extractor <b>118</b> may take on any non-planar or planar configuration known in the art or described in the present disclosure.

In another embodiment, the extractor opening <b>138</b> leads to one or more converging portions <b>140</b>. For example, the converging portion <b>140</b> may facilitate the transition between the extractor opening <b>138</b> and an opening slit <b>144</b>. In this regard, the converging portion <b>140</b> leads to the beam-defining aperture <b>142</b>, which may control the divergence and/or current of the electron beam <b>104</b>. In another embodiment, the beam-defining aperture <b>142</b> leads to the opening slit <b>144</b>. For example, the width of the extractor opening <b>138</b> may be larger than that of the opening slit <b>144</b>. In another embodiment, the electron beam <b>104</b> passes through the aperture <b>142</b> and to the emission cavity <b>146</b>.

Additionally, in this configuration, the majority of the electron beam <b>104</b> may terminate on the surfaces of the converging portion <b>140</b>. For example, up to 90% of the electron beam <b>104</b> from the emitter <b>108</b> may terminate at the one or more converging portions <b>140</b>. As a result, without mitigation, the electrons impinging on the surface of the extractor <b>118</b> continually cause desorption of contaminants.

In one embodiment, the one or more extractors <b>118</b> are formed from one or more getter materials. For example, the one or more extractors <b>118</b> may be formed from one or more non-evaporable getter materials. It is noted that by forming the one or more extractors <b>118</b> from one or more non-evaporable getter materials the stability of the emitter <b>108</b> (e.g., CNT emitter) may be improved through the continuous chemical absorption of the gaseous contaminants near the components of the electron source <b>102</b>. For instance, the continuous pumping provided by the extractor <b>118</b> formed from one or more non-evaporable getter materials may act to chemically absorb gaseous contaminants at or near the cathode of the electron source <b>102</b>, which is typically far removed from the primary pumping system of the electron-optical system <b>100</b>. In this regard, the getter material of the extractor <b>118</b> acts as a small pump with very high solid angle of collection of neutrals and charged ionic species in one of the most critical environments in the electron-optical system <b>100</b>.

Further, the geometry of the extractor <b>118</b>, such as, but not limited to, the extractor geometry shown in <figref idref="DRAWINGS">FIG. 1B</figref>, establishes the field necessary for field emission at the emitter <b>108</b> independent of the material used to form the extractor <b>118</b>.

The one or more getter materials may include any material suitable for absorbing one or more targeted contaminants. For instance, the one or more getter materials may be selected so as to chemically absorb one or more of the contaminants present within the electron-optical system <b>100</b>, such as, but not limited to, H₂, H₂O, CO, CO₂, O₂, N₂, NO, NO₂and the like. It is noted herein that the one or more contaminants may react with the one or more getter materials of the one or more extractors <b>118</b> to form a reaction product, such as, but not limited to, nonreactive metal oxides, carbides, and/or nitrides. In this regard, as the getter material is continually exposed to the contaminant materials, the getter material chemically reacts with the contaminant materials and forms a nonreactive compound, resulting in the uptake and sequestration of the contaminant material.

In one embodiment, the non-evaporable getter material used to form the one or more extractors <b>118</b> includes, but is not limited to, at least one of zirconium, vanadium, cobalt, aluminum, ruthenium, thorium, iron, molybdenum or boron. In another embodiment, the non-evaporable getter material includes a compound, mixture or alloy of one or more of zirconium, vanadium, cobalt, aluminum, ruthenium, thorium, iron, molybdenum or boron.

For example, the non-evaporable getter material may include, but is not limited to, a zirconium alloy. For instance, the non-evaporable getter material may include, but is not limited to, an alloy containing at least zirconium and titanium. In another instance, the non-evaporable getter material may include, but is not limited to, an alloy containing at least zirconium and vanadium, such as, but not limited to, St 707 (70% zirconium, 24.6% vanadium, and a balance of iron alloy). In another instance, the non-evaporable getter material may include, but is not limited to, an alloy containing at least zirconium and cobalt, such as, but not limited to, St 787 (80.8% zirconium, 14.2% cobalt, and mischmetal). In another instance, the non-evaporable getter material may include, but is not limited to, an alloy of at least zirconium and aluminum, such as, but not limited to, St 101 (84% zirconium and 16% aluminum).

It is further noted that the extractor <b>118</b> may be formed from a selected non-evaporable getter material so as to target a particular gaseous contaminant species for uptake. Table I below provides a list of example getter materials and the corresponding one or more gas species that the getter materials may effectively uptake.

<tables id="TABLE-US-00001" num="00001"><table frame="none" colsep="0" rowsep="0"><tgroup align="left" colsep="0" rowsep="0" cols="4"><colspec colname="offset" colwidth="14pt" align="left" /><colspec colname="1" colwidth="84pt" align="left" /><colspec colname="2" colwidth="42pt" align="left" /><colspec colname="3" colwidth="77pt" align="center" /><thead><row><entry /><entry namest="offset" nameend="3" rowsep="1">TABLE I</entry></row><row><entry /><entry namest="offset" nameend="3" align="center" rowsep="1" /></row><row><entry /><entry /><entry>Target</entry><entry>Getter capacity</entry></row><row><entry /><entry>Getter material</entry><entry>Gas species</entry><entry>(Pa-I/mg)</entry></row><row><entry /><entry namest="offset" nameend="3" align="center" rowsep="1" /></row></thead><tbody valign="top"><row><entry /></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="4"><colspec colname="offset" colwidth="14pt" align="left" /><colspec colname="1" colwidth="84pt" align="left" /><colspec colname="2" colwidth="42pt" align="left" /><colspec colname="3" colwidth="77pt" align="char" char="." /><tbody valign="top"><row><entry /><entry>Aluminum</entry><entry>O₂</entry><entry>1.0</entry></row><row><entry /><entry>Barium</entry><entry>CO₂</entry><entry>0.7</entry></row><row><entry /><entry /><entry>H₂</entry><entry>11.5</entry></row><row><entry /><entry /><entry>N₂</entry><entry>1.3</entry></row><row><entry /><entry /><entry>O₂</entry><entry>2.0</entry></row><row><entry /><entry>Magnesium</entry><entry>O₂</entry><entry>2.7</entry></row><row><entry /><entry>Rare Earth Elements</entry><entry>CO₂</entry><entry>0.3</entry></row><row><entry /><entry>(cerium, lanthanum)</entry><entry>H₂</entry><entry>6.1</entry></row><row><entry /><entry /><entry>N₂</entry><entry>0.4</entry></row><row><entry /><entry /><entry>O₂</entry><entry>2.8</entry></row><row><entry /><entry>Titanium</entry><entry>H₂</entry><entry>27.0</entry></row><row><entry /><entry /><entry>N₂</entry><entry>0.9</entry></row><row><entry /><entry /><entry>O₂</entry><entry>4.4</entry></row><row><entry /><entry namest="offset" nameend="3" align="center" rowsep="1" /></row></tbody></tgroup></table></tables>

It is noted that the listed of getter materials provided in Table I is not intended to be a limitation on the scope of the present disclosure and is provided merely for purposes of illustration. It is further noted that many getter reactions may be generalized as follows: <br />2GM+O₂→2GMO  (1)<br />2GM+N₂→2GMN  (2)<br />2GM+CO→GMC+GMO  (3)<br />2GM+CO₂→CO+2GMO→GMC+GMO  (4)<br />GM+H₂O→H+GMO→GMO+H (bulk)  (5)<br />GM+H₂→GMH+H (bulk)  (6)<br />GM+C_xH_y→GMC+H (bulk)  (7)<br />GM+Inert Gas (He, Ne, Ar, Kr, Xe)→No reaction  (8)<br /> where GM represents the given getter material.

In another embodiment, the extractor <b>118</b> may be formed from two or more non-evaporable getter materials in order to target two or more particular gaseous contaminant species.

The extractor <b>118</b> may be formed from a chosen getter material using any formation means known in the art. In one embodiment, the extractor <b>118</b> may be formed via one or more mechanical processes. For example, the extractor <b>118</b> may be formed from one or more mechanical processes including, but not limited to, a lathing process, a milling process, or a drilling process. In this regard, a bulk solid volume of the getter material may be supplied and one or more mechanical processes may be applied to the volume of getter material in order to achieve the extractor <b>118</b> having the desired shape/size.

In another embodiment, the extractor <b>118</b> may be formed via one or more casting processes. For example, a molten form of the getter material or precursor of the getter material may be suppled and poured into a mold of the extractor <b>118</b>. In another embodiment, the extractor <b>118</b> may be formed via one or more extrusion processes. For example, a solid volume of the getter material may be suppled and extruded through an extruder to achieve the extractor <b>118</b> having the desired shape/size.

In another embodiment, the extractor <b>118</b> may be formed via one or more powder metallurgical process, such as, but not limited to, a sintering process. In this regard, a volume of powdered getter material may be supplied and one or more sintering processes may be applied to achieve the extractor <b>118</b> having the desired shape/size.

In another embodiment, the extractor <b>118</b> may be formed via one or more optical processes, such as, but not limited to, laser ablation. In this regard, a bulk volume of the getter material may be supplied and one or more laser ablation processes may be applied to the volume of getter material to achieve the extractor <b>118</b> having the desired shape/size.

In another embodiment, the extractor <b>118</b> may be formed via one or more additive manufacturing processes. For example, the extractor <b>118</b> may be fabricated via a three-dimensional printing process. In this regard, getter material may be supplied and a 3-D printing tool may be used to form the extractor <b>118</b>. In another embodiment, a selective laser sintering process may be applied to form the extractor <b>118</b>. Selective laser sintering, used to three-dimensionally print materials, is generally described in U.S. Pat. No. 4,863,538, issued on Sep. 5, 1986, which is incorporated herein by reference in the entirety.

In another embodiment, the extractor <b>118</b> may be formed via one or more film formation processes. For example, as shown in <figref idref="DRAWINGS">FIG. 1C</figref>, one or more surface layers <b>147</b> of non-evaporable getter material may be deposited onto the surface of a substrate <b>149</b> to form the extractor <b>118</b>. Any film deposition process known in the art may be used to form the one or more layers <b>147</b>. For example, the one or more surface layers <b>147</b> may be deposited onto the substrate <b>149</b> using one or more of the methods including, but not limited to, sputtering, resistive evaporation, electron beam evaporation, vapor deposition, atomic layer deposition, electroplating, screen printing, solution casting or any other suitable deposition technique known in the art. The substrate <b>149</b> may include any substrate known in the art. For example, as discussed further herein, the substrate may include, but is not limited to, a substrate that is transparent to a selected wavelength (or range of wavelengths) of radiation. For instance, the substrate <b>149</b> may include a silicon substrate, which is transparent to 1064 nm light.

In another embodiment, as shown in <figref idref="DRAWINGS">FIG. 1D</figref>, the porosity of the body of the extractor <b>118</b> may be controlled during formation of the extractor <b>118</b>. It is noted that the uptake ability of a given extractor <b>118</b> is dependent on the porosity of the extractor <b>118</b>. In this regard, increased porosity provides for increased surface area (for absorbing contaminants) within the volume of the extractor <b>118</b>. In contrast, increased porosity also decreases the overall bulk volume of the extractor <b>118</b>, thereby reducing the ability of the extractor to “hold” or contain the absorbed contaminants. As a result, the extractor <b>118</b> may be formed with a selected porosity or within a selected porosity range, which serves to maximize uptake of one or more contaminants (or at least establishes uptake above a selected level). For example, the extractor <b>118</b> may be formed with a porosity of 0.05 to 0.95 of the theoretical density of the extractor <b>118</b>. For instance, the extractor <b>118</b> may be formed with a porosity of 0.2 to 0.8 of the theoretical density of the extractor <b>118</b>.

It is noted herein that any number of the fabrication techniques described above may be implemented to control porosity. In one embodiment, a sintering process utilizing a pore-forming step may be implemented to control the porosity of the extractor <b>118</b>. For example, a pore-forming material (e.g., polyethylene spheres) may be added to and mixed with a volume of powdered non-evaporable getter material. Then, the mixture may undergo a sintering process to a desired sintering temperature at a desired pressure. In another embodiment, during the heat treatment of the sintering process, the pore forming material is burned out of the extractor, leaving behind a set of pores <b>150</b> of desired number and size. In another embodiment, the porosity of the extractor <b>118</b> may be controlled precisely through an additive manufacturing technique, such as, but not limited to, three-dimensional printing or laser sintering. In this regard, the additive manufacturing process may be used to control the size, number and location of pores (or voids) <b>150</b> within the extractor <b>118</b>. In regard, the additive manufacturing process may form a regular or irregular pattern of getter material within the volume of the extractor <b>118</b>.

In another embodiment, the extractor <b>118</b> formed from NEG material is activatable. As noted previously herein, the extractor <b>118</b> passively chemically absorbs one or more reactive contaminants from the emission region <b>136</b> and the emission cavity <b>146</b>. The passive absorption of the extractor <b>118</b> may last for months. Further, the chemical absorption of reactive contaminants may be reversible. For example, an extractor <b>118</b> may be heated in order to chemically desorb contaminant material stored in the volume of the extractor <b>118</b>. In this regard, in order to activate an extractor <b>118</b> that has reduced absorption capabilities due to uptake, an activation procedure may be performed by heating the extractor <b>118</b> using one or more approaches. Further, heating the extractor <b>118</b> causes one or more contaminants (or compounds of contaminants) to desorb from the extractor <b>118</b>, allowing it to then be degassed by the system <b>100</b> when the system <b>100</b> is not in operation. For example, a heating process may be applied to heat the extractor to a temperature between 200 and 800° C. for a selected period of time (0.1 hours to 24 hours). It is noted herein that in some operation settings once the non-evaporable getter material of the extractor <b>118</b> is activated the system <b>100</b> may experience a temporary increase in pressure as chemisorbed species are liberated from the non-evaporable getter material. The liberated species may then be pumped out of the vacuum system of system <b>100</b> via traditional pumping means. Further, when cooled the non-evaporable getter material of the extractor <b>118</b> is cooled and the getter material begins to remove gasses and contaminants from the vacuum system of the system <b>100</b>.

It is noted that any heating process may be applied to the extractor <b>118</b> in order to activate the extractor <b>118</b>. In one embodiment, a resistive heating process may be applied to activate the extractor <b>118</b>. For example, as shown in <figref idref="DRAWINGS">FIG. 1E</figref>, one or more resistive heating devices <b>156</b> (e.g., resistive heating coils) may be disposed within or on the extractor <b>118</b> and used to selectively heat the extractor <b>118</b>. In another embodiment, control circuitry <b>158</b> may be used to control the operational state (e.g., ON/OFF state or temperature) of the resistive heating device <b>156</b> by controlling the current flowing through the device. Further, the one or more resistive heating devices may be used to activate the extractor <b>118</b> in-vacuo, eliminating the need to remove the extractor <b>118</b> from the system <b>100</b>.

In another embodiment, in cases where the one or more non-evaporable getter materials of the extractor <b>118</b> are metal, an inductive heating process may be applied to activate the extractor <b>118</b>. For example, as shown in <figref idref="DRAWINGS">FIG. 1F</figref>, one or more induction coils <b>161</b> may be inductively coupled to the metal non-evaporable getter material of the extractor <b>118</b>, whereby energy is then transferred to the metal non-evaporable material via magnetic field(s) <b>163</b> to heat the one or more non-evaporable getter materials. In another embodiment, control circuitry <b>159</b> may be used to control the operational state (e.g., ON/OFF state or magnetic flux) of the induction coil <b>161</b> by controlling the current flowing through the device. Further, the inductive heating process may be used to activate the extractor <b>118</b> in-vacuo, again eliminating the need to remove the extractor <b>118</b> from the system <b>100</b>. It is noted that the arrangement of the induction coil <b>161</b> is not intended to be a limitation on the present disclosure and is provided merely for illustrative purposes. It is recognized that any one or more induction coils, arranged in any geometrical relationship with the extractor <b>118</b> may be implemented in system <b>100</b>. In addition, the one or more induction coils <b>161</b> may be inductively coupled to multiple NEG electron-optical elements of the system <b>100</b>.

In another embodiment, the extractor <b>118</b> may be heated optically. For example, as shown in <figref idref="DRAWINGS">FIG. 1G</figref>, in cases where the non-evaporable getter material is a film layer deposited on a substrate, the substrate <b>149</b> may be chosen so it is transparent to a selected wavelength or wavelength range of light emitted by the light source <b>151</b>. For instance, the substrate may include, but is not limited to, a silicon substrate, which is transparent to light of 1064 nm. In this embodiment, a beam of 1064 nm light may pass through the substrate <b>149</b> and heat the non-evaporable getter material deposited on (or about) the underlying silicon substrate <b>149</b>. Further, optical heating may be used to activate the extractor <b>118</b> in-vacuo, again eliminating the need to remove the extractor <b>118</b> from the system <b>100</b>. It is noted herein that these activation examples should not be interpreted to limit the scope of the present disclosure and are provided merely for illustrative purposes.

In another embodiment, a heating process may be applied to the extractor <b>118</b> outside of the vacuum of system <b>100</b>. For example, a heating process may be applied with an oven to activate the extractor <b>118</b>. In this regard, the extractor <b>118</b> may be removed from the system <b>100</b> and heat-treated utilizing an oven. Once the heat treatment is complete, the extractor <b>118</b> may be returned to the system <b>100</b>.

While the present disclosure has focused on the implementation of one or more non-evaporable getter materials in the context of the extractor <b>118</b> of the electron source <b>102</b>, this should not be interpreted as a limitation on the scope of the present disclosure. Rather, the above description related to the extractor <b>118</b> is provided merely for illustrative purposes. It is contemplated herein that the principles described above may also be extended to one or more components of the electron-optical column <b>106</b> and/or the detector assembly <b>126</b> of system <b>100</b>.

<figref idref="DRAWINGS">FIG. 1F</figref> illustrates an electron-optical column <b>106</b> equipped with one or more electron-optical elements formed from one or more non-evaporable getter materials, in accordance with one or more embodiments of the present disclosure.

In one embodiment, as shown in <figref idref="DRAWINGS">FIG. 1H</figref>, the electron-optical column <b>106</b> includes one or more beam deflector elements <b>120</b>. The one or more beam deflector elements <b>120</b> (e.g., quadrupole deflectors or octupole deflectors) may be formed from one or more non-evaporable getter materials. It is noted that the one or more deflector elements <b>120</b> may be formed by any of the methods and with any of the non-evaporable getter materials described previously herein.

In another embodiment, as shown in <figref idref="DRAWINGS">FIG. 1I</figref>, the electron-optical column <b>106</b> includes one or more astigmatism compensators <b>166</b> or stigmators. The one or more astigmatism compensators may be formed by any of the methods and with any of the non-evaporable getter materials described previously herein.

In another embodiment, as shown in <figref idref="DRAWINGS">FIG. 1J</figref>, the electron-optical column <b>106</b> includes one or more current or beam limiting apertures <b>168</b>. In one embodiment, the one or more current or beam limiting apertures <b>168</b> may consist of a disc or foil shape including one or more holds for passage of the electron beam <b>104</b>. The holes may have any shape known in the art. For example, the holes may be circular, square, rectangular or any other shape for projecting a shaped spot onto the sample <b>110</b>. The one or more current or beam limiting apertures may be formed by any of the methods and with any of the non-evaporable getter materials described previously herein.

In another embodiment, as shown in <figref idref="DRAWINGS">FIG. 1K</figref>, the electron-optical column <b>106</b> includes a soft electron extractor <b>170</b> (or Wehnelt electrode). It is noted that the soft electron extractor <b>170</b> may face the sample surface. For instance, in the case of semiconductor fabrication, the sample surface may consist of a bare or resist coated semiconductor wafer. It is further noted that a resist coated semiconductor wafer may serve as significant contamination source. It is recognized herein that an active pumping element, such as the soft electron extractor <b>170</b> formed from non-evaporable getter material, placed in this would serve to reduce contamination of the surfaces facing the return beam path <b>124</b>. The one or more soft electron extractors may be formed by any of the methods and with any of the non-evaporable getter materials described previously herein.

It is further noted that the set of electron-optical elements of the electron-optical column <b>106</b> may include any additional electron-optical elements known in the art suitable for focusing and/or directing the electron beam <b>104</b> onto a selected portion of the sample <b>110</b>. In one embodiment, the set of electron-optical elements includes one or more electron-optical lenses. For example, the set of electron-optical elements may include one or more condenser lenses <b>114</b>. By way of another example, the set of electron-optical elements includes one or more objective lenses <b>116</b>. The one or more condenser lenses and one or more objective lenses may include any lens technology known in the art of electron-optics capable of shaping the electron beam <b>104</b>.

The electron detector assembly <b>126</b> includes any detector technology known in the art capable of detecting electrons <b>124</b> emanating from the sample <b>110</b> (e.g., secondary electrons and/or backscattered electrons). For example, a secondary electron detector may include an electron collector, which collects secondary electrons <b>124</b> emitted by the surface of the sample <b>110</b>. Further, the electron detector assembly <b>126</b> may include a detector for detecting the secondary electrons <b>124</b>. For instance, the electron detector assembly <b>126</b> may include, but is not limited to, an Everhart-Thornley detector. By way of another example, the detector element may include, but is not limited to, a scintillating element and PMT detector. In another embodiment, the detector assembly <b>126</b> may include one or more of micro-channel plate (MCP), a PIN or p-n junction detector, such as a diode or a diode array or one or more avalanche photo diodes (APDs). In one embodiment, one or more portions of the detector assembly <b>126</b> may include one or more non-evaporable getter materials. For instance, as shown in <figref idref="DRAWINGS">FIG. 1L</figref>, the housing of the detector assembly <b>126</b> may be coated in or formed from a non-evaporable getter material <b>172</b>.

<figref idref="DRAWINGS">FIG. 1M</figref> illustrates an in-column electron detector configuration, in accordance with one or more embodiments of the present disclosure. In one embodiment, the electron detector <b>126</b> is positioned within (or below) the electron-optical column <b>106</b>. In this example, backscattered and/or secondary electrons <b>124</b> may be collected and imaged using one or more of micro-channel plate (MCP), a PIN or p-n junction detector, such as a diode or a diode array or one or more avalanche photo diodes (APDs). In one embodiment, one or more components of the in-column electron detector assembly <b>126</b>, as shown in <figref idref="DRAWINGS">FIG. 1M</figref>, are coated or formed from non-evaporable getter materials. For instance, the detector region of the detector assembly <b>126</b> may be surrounded by a cylindrical wall <b>174</b> formed from non-evaporable getter material.

The one or more components of the electron detector assembly <b>126</b> may be formed by any of the methods and with any of the non-evaporable getter materials described previously herein.

<figref idref="DRAWINGS">FIG. 2</figref> illustrates a process flow diagram depicting a method <b>200</b> for forming an electron-optical element from a non-evaporable getter element, in accordance with one or more embodiments of the present disclosure. It is noted herein that the various embodiments, components and architecture described previously herein should be interpreted to extend to the method <b>200</b> of <figref idref="DRAWINGS">FIG. 2</figref>.

In step <b>202</b>, a non-evaporable getter material or a precursor of the non-evaporable getter material is provided. In one embodiment, the non-evaporable getter material includes, but is not limited to, at least one of zirconium, vanadium, cobalt, aluminum, ruthenium, thorium, iron, molybdenum or boron. In another embodiment, the non-evaporable getter element is formed from a non-electrically conductive material. In another embodiment, the non-evaporable getter element is formed from an electrically conductive material.

In a second step <b>204</b>, an electron-optical element is formed from the non-evaporable getter material or the precursor of the non-evaporable getter material. The non-evaporable getter element may be formed by any fabrication process known in the art, such as, but not limited to, one or more mechanical processes, one or more powder metallurgical processes, one or more casting processes, one or more extrusion process, one or more optical processes, one or more additive manufacturing processes, and the like.

In another embodiment, the electron-optical element formed from a non-evaporable getter material includes one or more electron-optical elements of the electron source <b>102</b>. For example, the one or more electron-optical elements of the electron source <b>102</b> may include, but are not limited to, one or more extractors <b>118</b>.

In another embodiment, the electron-optical element formed from a non-evaporable getter material includes one or more electron-optical elements of the electron-optical column <b>106</b>. For example, the one or more electron-optical elements of the electron-optical column <b>106</b> may include, but are not limited to, one or more of a deflector, a current limiting aperture, an astigmatism compensator, a soft extractor or the like.

It is believed that the present disclosure and many of its attendant advantages will be understood by the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the components without departing from the disclosed subject matter or without sacrificing all of its material advantages. The form described is merely explanatory, and it is the intention of the following claims to encompass and include such changes.